This invention relates to photocopying machines; and, more particularly, to the adjustable support for the corona assemblies which induce charge onto and neutralize charge on the photosensitive member used in such machines.
Typical photocopying machines have a revolving photosensitive drum which can accept and hold an electric charge. In operation, the drum surface is initially uniformly charged and thereafter selectively discharged according to the image to be copied. This selective discharge therefore leaves on the photosensitive drum an array of electric charges which form a latent image of the material to be copied. This latent image of electric charges is then exposed to oppositely charged toner particles which adhere to the photosensitive drum, thereby developing the image. This developed image is subsequently transferred to the surface of a copy sheet. After a copy has been made, the photosensitive drum is uniformly discharged in preparation for the next copy.
The electric charges are induced onto the photosensitive revolving drum by means of a corona assembly. A corona assembly usually includes at least one long, thin wire shielded on three sides by a metal channel. The corona assembly is maintained near the surface of the photosensitive drum. A sufficiently high voltage is applied to the wire to ionize the surrounding air and to induce electric charges onto the surface of the photosensitive drum. The amount of charge so induced is very sensitive to the distance of the corona wire from the surface of the photosensitive drum. Because of the manufacturing tolerances inherent in the mass production of photocopying machines, the distance between the corona wire and the surface of the photosensitive drum generally is adjustable after manufacture so that the proper voltage will be induced onto the surface of the photosensitive drum.
In the past according to one commercial practice, the corona wire has been mounted so that its position within the metal channel is adjustable, thereby allowing the distance between the wire and the photosensitive drum to be varied to a desired value. This method of mounting the corona wire so that its distance from the photosensitive drum surface can be adjusted makes adjustment difficult because it requires that the corona assembly be removed and adjustment cannot be made while the machine is running.
Accordingly, it is an object of the present invention to provide an adjustable support for the corona assembly which allows the simple, sure and efficient setting of the proper distance between the corona assembly wire and the surface of the photosensitive drum during machine operation if desired.
It is a further object of this invention to provide an adjustable support which securely locks the corona assembly in the proper location after the separation between the corona wires and the photosensitive surface has been adjusted.